This invention relates to an apparatus for detection of the properties of individual ions.
Detectors of charged particles have been produced for years in many forms to detect various properties of charged particles. One particular type of interest is a detector for placement at the focal surface of a magnetic spectrograph. The magnetic spectrograph bends the paths of moving charged particles in a magnetic field so that the product of the magnetic flux density and the radius of curvature of the path of a charged particle is proportional to the momentum of the particle. All particles are focused on a focal surface, and the position along the focal surface provides a measure of the momentum of a moving particle. If one additional property such as the energy or velocity can be deduced by a detector, it is possible to identify the mass of the particle and hence what the particle is. The selectivity of such a detector becomes particularly important when heavy ions (defined as those greater than 10 atomic mass units) are studied because the percent differences between isotopes of adjacent mass numbers become smaller as the mass increases. One instrument designed for such measurements is the position-sensitive double proportional counter which measures the position of a particle along the focal surface, the energies of a number of particles and the final energy of the particle. Another instrument useful for such measurements is the so-called delta E-E time-of-flight telescope, which measures the product of energy loss (delta E) and energy (E). Other instruments are known that are useful for measuring properties of charged particles but that are of less direct use in application to a magnetic spectrograph. All of the instruments that have been known previously are inadequate for measuring properties of heavy ions at the focal surface of a magnetic spectrograph. Some do not provide adequate resolution of the energies of particles. Others do not provide means of measuring the angle of incidence of a particle. They do not provide for a multiple measurement of the energy change as the particle is stopped.
It is an object of the present invention to provide a better focal-surface detector of charged particles.
It is a further object of the present invention to provide a detector for placement at the focal surface of a magnetic spectrograph.
It is a further object of the present invention to provide a focal-surface detector for heavy ions having having improved discrimination between particles.
It is a further object of the present invention to provide a detector of charged particles that is sensitive to the position of the charged particles in a focal surface.
Other objects will become apparent in the course of a detailed description of the invention.